This invention is in the field of alveolar bone measurement for the drilling of an implant receiving cavity for tooth replacement purposes. In particular the invention is concerned with aiding in determining the drilling depth of the implant receiving cavity in the alveolar bone.
Endosseous osseointegrated, root form implants are employed for tooth replacement in both the posterior mandible and the posterior maxilla. Before commencing drilling of an implant receiving cavity, an investigation is made to determine the length of the longest physiologically possible implant which can be safely implanted whilst leaving sufficient alveolar bone tissue of about 2 mm either above the superior border of the mandibular canal in a posterior mandible, or below the inferior surface of the maxillary sinus in a posterior maxilla, through which the plexus of nerves extends. Hereinafter in the specification and claims, the term canal refers to the mandibular canal and to the posterior maxilla. Being more practical, it denotes a non-bone tissue within the posterior mandible and the posterior maxilla, respectively.
Such investigations arc typically performed by way of panoramic X-ray radiography technique or, more occasionally, CT dental scans. To avoid possible puncturing of either a mandibular canal or a maxillary sinus, shorter implants than physiologically safe are typically employed which reduces osseointegration, with surrounding bone tissue thereby militating against successful implantation.
It is also of significance that the condition of the posterior mandible and the posterior maxilla be assessed prior to drilling an implant receiving cavity, in order to determine whether the bone is suitable for receiving an implant and to avoid unnecessary surgical performance. Such assessment may be carried out by examining the porosity of the bone tissue.
Thus, it is an object of the present invention to provide a method and a system for assessing the condition of a bone tissue, prior to drilling in the alveolar bone, and for assessing the depth remaining between an end wall of an implant receiving cavity and a non-bone tissue, namely a canal within the alveolar bone.
The term area of interest as used in the specification and claims, is used to denote the location at which a ultrasound probe is located, either over skin tissue, or on the bone surface (prior to drilling) or within a bore of the implant receiving cavity.
In accordance with the present invention, there is provided an ultrasound system for assessment of distance between an area of interest and a known location of a non-bone canal for use in drilling an implant receiving cavity in the alveolar bone of a human subject""s posterior mandible or posterior maxilla, the system comprising:
(a) an ultrasound probe capable of being introduced at the area of interest and transceiving pulse echo ultrasound signal to the alveolar bone and therefrom; and
(b) an electronic circuitry for processing the ultrasound signal, for providing an indication of the remaining alveolar bone distance between said ultrasound probe and a canal within the alveolar bone.
The present invention enables intraoperative determination of the length of the longest endosseous osseointegrated root form implant which can be safely implanted, thereby facilitating a more accurate procedure rather than hitherto available. The indication can be either an actual alveolar bone distance measurement, whereupon an implant receiving cavity can be further deepened until a recognized minimum thickness of alveolar bone remains. Alternatively, a warning indication can be provided when a predetermined minimum alveolar bone distance is reached whereupon the drilling of an implant receiving cavity is terminated. Either technique is suitable for tooth replacement in either a posterior mandible or a posterior maxilla.
The system of the present invention is useful also in accessing the condition (quality) of the alveolar bone, namely if performing an implant receiving cavity may be considered in light of the bones condition. This may be carried out prior to drilling by inserting the probe over either over skin tissue or on the bone surface prior to drilling and performing the procedure of steps (a) and (b) above.